Method and system for recovering and purifying a gaseous sterilizing agent

ABSTRACT

A system and method for recovering a sterilization agent from waste gaseous mixture, comprising a gas separator to wash waste gas comprising a gaseous mixture of a sterilization agent, insert dilution gases, and water vapor, from plurality sterilization chambers, with water, thereby producing a water-gaseous sterilization agent mixture collected at bottom section of the gas separator, and inert dilution gases exhausted at top section of the gas separator; a pressure reducing valve; a first tank or gas evaporator to produce gaseous sterilization agent and water vapor; a first condenser to produce condensed water vapor and separate the gaseous sterilization agent from the condensed water vapor; a water tank to receive the condensed water vapor; a separation pump for raising pressure of the gaseous sterilization agent; a second condenser to cool the gaseous sterilization agent causing the sterilization agent to condense into liquid; and a second tank for storing the liquid sterilization agent.

FIELD OF THE DISCLOSURE

The present disclosure relates to gaseous sterilization agents, and morespecifically to a method and system for recovering and purifying agaseous sterilization agent.

BACKGROUND

Ethylene oxide (ETO) is a highly reactive organic compound whose highreactivity makes it useful in many different applications. Due to thehigh reactivity of ETO, ETO may be used as a surface disinfectant, orsterilizing agent. ETO as a sterilizing agent is well known for itseffectiveness to sterilize objects at certain gas concentrations. Theobjects for sterilization are placed in a hermitically sealed chamber.ETO vapor is then pumped into the chamber to sterilize the objects.

However, due to the high reactivity, ETO gas is extremely flammable,toxic, and explosive. Even in the absence of air, ETO must be used withextreme caution in high concentrations at low pressures forsterilization purposes. Presently, high concentration ETO gas is notrecyclable and may be used only once. After use, the ETO gas is thendischarged to an emission control device for destruction.

There are a few current approaches for addressing the problem ofemission and disposal of the ETO toxic gas, which solves one problem inexchange for creating another problem. For example, if ETO is absorbedinto water, then the problem then becomes the treatment and discharge ofthe toxic water. If one tries to dispose of ETO by combustion means, theproblem then becomes how to prevent an explosion (e.g., prevent anexplosive reaction).

One method for reusing ETO gas involves the use of a low concentrationmixture of ETO and an inert gas at higher process pressures. Highprocess pressures (e.g., up to 4 atmospheres) allow an increase in theETO gas concentration to an acceptable milligram per liter value foreffective sterilization. Mixtures having ratios of ETO to inert gas of10/90 and 20/80 are generally used. These mixtures have sufficient ETOconcentrations to sterilize objects regardless of the material beingsterilized under normal temperature and at above atmospheric pressureconditions. Relative non-flammability of diluted ETO and inert gasmixtures allows for the recycling of these mixtures. However, thesemixtures are not as effective as higher concentrations of ETO gas forsterilization.

In addition, the concentration of ETO decreases with continual useduring the sterilization process since ETO is consumed in reacting withbacteria, water vapor, alcohol and the like during the sterilizationprocess. Furthermore, the ETO gas concentration may be reduced to anunsatisfactory concentration level to provide a consistent sterilizationeffect. Thus, low concentration gas mixtures require processing usinghigher pressure rated vessels, which are more expensive. This processfurther involves processing the gases at above atmospheric pressureswhich carries the risk of fugitive and catastrophic leakage.Consequently, in the industry today, all large ETO sterilizer chambersare designed to operate using low pressure and high concentrations ofETO gas. Existing sterilizers in use in the industry are not rated forthe higher pressures that are required to recycle the low concentrationETO gas sterilant.

Thus, it is desirable to provide a system and method for recyclingsterilant gas mixtures to a high concentration of ETO gas to obtainmaximum sterilization effectiveness while minimizing the complexity ofthe process and the cost of the sterilization equipment. It is desirableto provide a system that can be retrofitted to existing sterilizationfacilities, by the utilization of the existing sterilization processequipment and avoiding the expenses that are associated with completesystem replacement.

Furthermore, when several large sterilization chambers are coupledtogether at the exhaust, as often the case in large commercialsterilization facilities, it is possible for the multiple chambers toexhaust waste gas stream simultaneously. This causes the peak flow rateof the resulting total waste gas stream to become multiple times greaterthan the flow rate if the waste gas stream is exhausted from a singlesterilization chamber. Therefore, in order to process the greater flowof waste gas stream for recycling sterilant gas to a high concentration,a correspondingly larger sized system is required.

A larger sized apparatus would mean increased size of the condensers,separation pump, piping, valves as well as the cooling systems thatcools the condensers. Hence, the initial capital cost would besignificantly increased to procure and install such large sizedapparatus, as would the costs for handling and operating such a largesized apparatus, specifically with respect to high cooling costs. Inaddition, space required for the installation would also be increased,which might be problematic for existing facilities where available spaceis already limited.

Therefore, it is desirable to limit the size increase of the recyclingapparatus when handling excessively large waste gas stream flow, and tolimit the cooling energy consumption of the recycling apparatus whenhandling excessively large waste gas stream flow.

SUMMARY

There is thus provided, in accordance with some embodiments of thepresent disclosure, a system for recovering a sterilization agent from awaste gaseous mixture may include a pressure reducing valve for reducinga pressure of a waste gas from one or more sterilization chambers to afirst predefined pressure. The waste gas may include a gaseous mixtureof a sterilization agent, nitrogen gas, and water vapor. A firstcondenser may be configured to receive the gaseous mixture via thepressure reducing valve, and to cool the gaseous mixture to atemperature below a boiling point temperature and above a freezing pointtemperature of the water vapor at the first predefined pressure. A firsttank, coupled to the first condenser, may store the condensed watervapor separated from the gaseous mixture in the first condenser. Aseparation pump coupled to the first tank may raise the pressure of thegaseous mixture to a second predefined pressure. A second condenser maybe configured to receive the gaseous mixture from the separation pump,to cool the gaseous mixture to a temperature below a boiling pointtemperature and above a freezing point temperature of the sterilizationagent at the second predefined pressure causing the sterilization agentto condense into a liquid, and to discharge the nitrogen gas remainingin the gaseous mixture. A second tank, coupled to the second condenser,may store the sterilization agent separated from the gaseous mixture inthe second condenser.

Furthermore, in accordance with some embodiments of the presentdisclosure, the sterilization agent may include ethylene oxide (ETO).

Furthermore, in accordance with some embodiments of the presentdisclosure, the first predefined pressure may be 1 pound per square inchand the second predefined pressure is atmospheric pressure.

Furthermore, in accordance with some embodiments of the presentdisclosure, the boiling point temperature of the water vapor may be 20deg C. when the pressure of the gaseous mixture is 1 psi.

Furthermore, in accordance with some embodiments of the presentdisclosure, boiling point temperature of the ETO may be 10 deg C. whenthe pressure of the gaseous mixture is atmospheric pressure.

Furthermore, in accordance with some embodiments of the presentdisclosure the sterilization agent may be propylene oxide.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may include a chamber evacuation pump coupled tothe pressure reducing valve for pumping the waste gas into the firstcondenser.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may include an exhaust warmer and a freezereconomizer for recovering cooling energy in the system.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may include one or more H₂O freezers coupled tothe first condenser and the separation pump, and wherein each of the oneor more H₂O freezers may freeze H₂O molecules in the water vapor to afreezer surface.

Furthermore, in accordance with some embodiments of the presentdisclosure, at least two H₂O freezers from the one or more H₂O freezersmay be connected in parallel coupled between the first condenser and theseparation pump.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may include an ETO freezer coupled to the secondcondenser for trapping residual vapors of the sterilization agent.

Furthermore, in accordance with some embodiments of the presentdisclosure the system may include a waste gas holding tank coupled tothe pressure reducing valve and to the one or more sterilizationchambers for collecting the waste gas from the one or more sterilizationchambers.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may include one or more ETO pre-condensers placedin series before the second condenser, wherein each of the one or morepre-condensers may have progressively lower temperatures above thetemperature of the second condenser.

There is further provided, in accordance with some embodiments of thepresent disclosure, a method for recovering a sterilization agent from awaste gaseous mixture that may include receiving a waste gas from asterilization chamber. The waste gas may include a gaseous mixture of asterilization agent, nitrogen gas, and water vapor, A pressure of thegaseous mixture may be reduced to a first predefined pressure so as toreduce a boiling point temperature of the sterilization agent to belowthe freezing point temperature of the water vapor in the gaseousmixture. The gaseous mixture with the pressure at the first predefinedpressure may be cooled to a temperature below a boiling pointtemperature and above the freezing point temperature of the water vapor.Condensed water vapor may be removed from the gaseous mixture. Thepressure of the gaseous mixture may be raised to a second predefinedpressure greater than the first predefined pressure so as to elevate aboiling point temperature of the sterilization agent in the gaseousmixture. The gaseous mixture at the second predefined pressure may becooled to a temperature below the boiling point temperature and above afreezing point temperature of the sterilization agent causing thesterilization agent to condense into a liquid. The liquid sterilizationagent may be separated from the gaseous mixture so as to recover thesterilization agent for reuse from the waste gas. The nitrogen gasremaining in the gaseous mixture may be discharged.

Furthermore, in accordance with some embodiments of the presentdisclosure, the sterilization agent may include ethylene oxide (ETO).

Furthermore, in accordance with some embodiments of the presentdisclosure, the first predefined pressure may be 1 pound per square inch(psi) and the second predefined pressure may be atmospheric pressure.

Furthermore, in accordance with some embodiments of the presentdisclosure, the boiling point temperature of the water vapor may be 20deg C. when the pressure of the gaseous mixture is 1 psi.

Furthermore, in accordance with some embodiments of the presentdisclosure, the boiling point temperature of the ETO may be 10 deg C.when the pressure of the gaseous mixture is atmospheric pressure.

Furthermore, in accordance with some embodiments of the presentdisclosure, the sterilization agent may be propylene oxide.

Furthermore, in accordance with some embodiments of the presentdisclosure, discharging the nitrogen gas may include discharging thenitrogen gas to the atmosphere or collecting the discharged nitrogen asfor reuse.

Furthermore, in accordance with some embodiments of the presentdisclosure, the method may include recovering cooling energy in thesystem by using; an exhaust warmer and a freezer economizer.

Furthermore, in accordance with some embodiments of the presentdisclosure, the method may include freezing H₂O molecules in the watervapor to a freezer surface of one or more H₂O freezers.

Furthermore, in accordance with some embodiments of the presentdisclosure, at least two H₂O freezers from the one or more H₂O freezersmay be connected in parallel, and the method may include defrosting atleast one of the H₂O freezers from the at least two parallel H₂Ofreezers.

Furthermore, in accordance with some. embodiments of the presentdisclosure, the method may include trapping residual vapors of thesterilization agent using, one or more ETO freezers coupled to thesecond condenser

Furthermore, in accordance with some embodiments of the presentdisclosure, at least two ETO freezers from the one or more FLO freezersmay be connected in parallel, and the method may include defrosting atleast one of the ETO freezers from the at least two parallel ETOfreezers.

Furthermore, in accordance with some embodiments of the presentdisclosure, the method may include collecting the waste gas from the oneor more sterilization chambers in a waste gas holding tank.

Furthermore, in accordance with some embodiments of the presentdisclosure, the method ma include setting the temperatures of each ofone or more ETO pre-condensers placed in series before the secondcondenser to progressively lower temperatures above the temperature ofthe second condenser.

There is further provided, in accordance with the present disclosure, asystem for recovering a sterilization agent from a waste gaseousmixture, the system may include a gas separator configured to wash wastegas from one or more sterilization chambers, with water, the waste gascomprising a gaseous mixture of a sterilization agent, inert dilutiongases, and water vapor, thereby the gaseous sterilization agent andwater vapor are absorbed by the water creating a water-gaseoussterilization agent mixture that is collected at a bottom section of thegas separator, and the inert dilution gases are exhausted at a topsection of the gas separator; a pressure reducing valve for reducing apressure of the water-gaseous sterilization agent mixture to a firstpredefined pressure; a first tank or a gas evaporator, coupled to thepressure reducing valve, configured to receive the water-gaseoussterilization agent mixture, and to heat the water-gaseous sterilizationagent mixture to a temperature above boiling point temperature of thesterilization agent and above a freezing point temperature of the waterto produce gaseous sterilization agent and water vapor; a firstcondenser configured to receive gaseous sterilization agent and watervapor via the first tank or the gas evaporator, and to cool the gaseoussterilization agent and water vapor to a temperature below a boilingpoint temperature and above a freezing point temperature of the watervapor at the first predefined pressure to produce condensed water vaporand to separate the gaseous sterilization agent from the condensed watervapor; a water tank, coupled to the first condenser, configured toreceive the condensed water vapor, wherein when the first tank heats thewater-gaseous sterilization agent mixture, the water tank is the sametank as the first tank, and when the gas evaporator heats thewater-gaseous sterilization agent mixture, the water tank is in additionto the first tank; a separation pump coupled to the first condenser forraising the pressure of the gaseous sterilization agent to a secondpredefined pressure;

a second condenser, configured to receive the gaseous sterilizationagent from the separation pump, to cool the gaseous sterilization agentto a temperature below a boiling point temperature and above a freezingpoint temperature of the sterilization agent at the second predefinedpressure causing the sterilization agent to condense into a liquid; anda second tank, coupled to the second condenser, for storing the liquidsterilization agent.

Furthermore, in accordance with some embodiments of the presentdisclosure, the sterilization agent may comprise ethylene oxide (ETO).

Furthermore, in accordance with some embodiments of the presentdisclosure, the first predefined pressure may be 1 pound per square inchand the second predefined pressure may be atmospheric pressure.

Furthermore, in accordance with some embodiments of the presentdisclosure the boiling point temperature of the water vapor may be 20deg C. when the pressure of the gaseous mixture is 1 psi.

Furthermore, in accordance with some embodiments of the presentdisclosure, the boiling point temperature of the ETO may be 10 deg C.when the pressure of the gaseous mixture is atmospheric pressure.

Furthermore, in accordance with some embodiments of the presentdisclosure, the sterilization agent may be propylene oxide.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may further comprise a chamber evacuation pumpcoupled to the gas separator for pumping the waste gas into the gasseparator.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may further comprise an exhaust warmer and afreezer economizer for recovering cooling energy in the system.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may further comprise one or more H₂O freezerscoupled to the first condenser and the separation pump, and wherein eachof the one or more H₂O freezers freezes H₂O molecules in the water vaporto a freezer surface.

Furthermore, in accordance with some embodiments of the presentdisclosure, at least two H₂O freezers from the one or more H₂O freezersmay be connected in parallel, coupled between the first condenser andthe separation pump.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may further comprise one, or more ETO freezerscoupled to the second condenser for trapping residual vapors of thesterilization agent.

Furthermore, in accordance with some embodiments of the presentdisclosure, at least two ETO freezers from the one or more ETO freezersmay be connected in parallel.

Furthermore, in accordance with some embodiments of the presentdisclosure, the system may further comprise one or more ETOpre-condensers placed in series before the second condenser, whereineach of the one or more pre-condensers may have progressively lowertemperatures above the temperature of the second condenser.

There is further provided, in accordance with the present disclosure, amethod for recovering a sterilization agent from a waste gaseousmixture, the method may include receiving a waste gas from one or moresterilization chambers, the waste gas comprising a gaseous mixture of asterilization agent, inert dilution gases, and water vapor; washing thegaseous mixture with water by a gas separator, thereby absorbing thesterilization agent and water vapor in the water, creating awater-gaseous sterilization agent mixture; collecting the water-gaseoussterilization agent mixture at a bottom section of the gas separator,and exhausting the inert dilution gases at a top section of the gasseparator; reducing a pressure of the water-gaseous sterilization agentmixture to a first predefined pressure so as to reduce a boiling pointtemperature of the sterilization agent to below a freezing pointtemperature of water in the water-gaseous sterilization agent mixture;heating the water-gaseous sterilization agent mixture to a temperatureabove boiling point temperature of the sterilization agent and above afreezing point temperature of the water to produce gaseous sterilizationagent and water vapor; cooling the gaseous sterilization agent and watervapor with the pressure at the first predefined pressure by a firstcondenser, to a temperature below a boiling point temperature and abovethe freezing point temperature of the water vapor, and removingcondensed water vapor from the gaseous sterilization agent; raising thepressure of the gaseous sterilization agent by a separation pump, to asecond predefined pressure greater than the first predefined pressure soas to elevate a boiling point temperature of the sterilization agent,said separation pump being coupled to the first condenser, or the upperportion of the first tank; cooling, the gaseous mixture at the secondpredefined pressure, by a second condenser, to a temperature below thebailing point temperature and above a freezing point temperature of thesterilization agent causing the sterilization agent to condense into aliquid, thereby collecting the liquid sterilization agent for reuse.

Furthermore, in accordance with some embodiments of the presentdisclosure, the sterilization agent may comprise ethylene oxide (ETO).

Furthermore, in accordance with some embodiments of the presentdisclosure, the first predefined pressure may be 1 pound per square inch(psi) and the second predefined pressure may be atmospheric pressure.

Furthermore, in accordance with some embodiments of the presentdisclosure, the boiling point temperature of the water vapor may be 20deg C. when the pressure of the gaseous mixture is 1 psi.

Furthermore, in accordance with some embodiments of the presentdisclosure, thee boiling point temperature of the ETO may be 10 deg C.when the pressure of the gaseous mixture is atmospheric pressure.

Furthermore, in accordance with some embodiments of the presentdisclosure, the sterilization agent may be propylene oxide.

Furthermore, in accordance with some embodiments of the presentdisclosure, the exhausting inert dilution gases may comprise dischargingnitrogen gas or CO₂ gas or a combination thereof, to the atmosphere orcollecting the exhausted inert dilution gases comprising nitrogen gas orCO₂ gas or a combination thereof, for reuse.

Furthermore, in accordance with some embodiments of the presentdisclosure, the method may further comprise recovering cooling energy inthe system by using an exhaust warmer and a freezer economizer.

Furthermore, in accordance with some embodiments of the presentdisclosure, the method may further comprise freezing H₂O molecules inthe water vapor to a freezer surface of one or more H₂O freezers.

Furthermore, in accordance with some embodiments of the presentdisclosure, at least two H₂O freezers from the one or more H₂O freezersmay be connected in parallel, and further comprising defrosting at leastone of the freezers from the at least two parallel H₂O freezers.

Furthermore, in accordance with some embodiments of the presentdisclosure, the method may further comprise trapping residual vapors ofthe sterilization agent using one or more ETO freezers coupled to thesecond condenser.

Furthermore, in accordance with some embodiments of the presentdisclosure, at least two ETO freezers from the one or more H₂O freezersmay be connected in parallel, and further comprising defrosting at leastone of the ETO freezers from the at least two parallel ETO freezers.

Furthermore, in accordance with some embodiments of the presentdisclosure, the method may further comprise setting the temperatures ofeach of one or more ETO pre-condensers placed in series before thesecond condenser to progressively lower temperatures above thetemperature of the second condenser.

BRIEF DESCRIPTION OF THE DRAWINGS

In order for the embodiments of the present disclosure to be betterunderstood and for its practical applications to be appreciated, thefollowing Figures are provided and referenced hereafter. It should benoted that the Figures are given as examples only and in no way limitthe scope of the embodiments of the present disclosure. Like componentsare denoted by like reference numerals.

FIG. 1 schematically illustrates a block diagram of a first embodimentof a system for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure;

FIG. 2 schematically illustrates a block diagram of a second embodimentof a system for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure;

FIG. 3 schematically illustrates a block diagram of a third embodimentof a system for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure;

FIG. 4 schematically illustrates a block diagram of a fourth embodimentof a system for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure;

FIG. 5 schematically illustrates a block diagram of a fifth embodimentof a system for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure;

FIG. 6 schematically illustrates a block diagram of a sixth embodimentof a system for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure;

FIG. 7 is a flowchart depicting a method for recovering a sterilizationagent from a waste gaseous mixture, in accordance with some embodimentsof the present disclosure;

FIG. 8 schematically illustrates a block diagram of an embodiment of asystem for recovering a sterilization agent from a waste gaseous mixturefrom one or more sterilization chambers, in accordance with someembodiments of the present disclosure;

FIG. 9 schematically illustrates a block diagram of an embodiment of asystem for recovering a sterilization agent from a waste gaseous mixturefrom one or more sterilization chambers, in accordance with someembodiments of the present disclosure; and

FIG. 10 is a flowchart depicting a method for recovering a sterilizationagent from a waste gaseous mixture from one or more sterilizationchambers, in accordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the embodiments ofthe disclosure. However, it will be understood by those of ordinaryskill in the art that the embodiments of the disclosure may be practicedwithout these specific details. In other instances well-known methods,procedures, components, modules, units and/or circuits hake not beendescribed in detail so as not to obscure the embodiments of thedisclosure.

Although embodiments of the disclosure are not limited in this regard,discussions utilizing terms such as, for example, “processing,”“computing,” “calculating,” “determining,” “establishing”, “analyzing”,“checking”, or the like, may refer to operation(s) and/or process(es) ofa computer, a computing platform, a computing system, or otherelectronic computing device, that manipulates and/or transforms datarepresented as physical (e.g., electronic) quantities within thecomputer's registers and/or memories into other data similarlyrepresented as physical quantities within the computer's registersand/or memories OT other information non-transitory storage medium(e.g., a memory) that may store instructions to perform operationsand/or processes. Although embodiments of the disclosure are not limitedin this regard, the terms “plurality” and “a plurality” as used hereinmay include, for example, “multiple” or “two or more”. The terms“plurality” or “a plurality” may be used throughout the specification todescribe two or more components, devices, elements, units, parameters,or the like. Unless explicitly stated, the method embodiments describedherein are not constrained to a particular order or sequence.Additionally, some of the described method embodiments or elementsthereof can occur or be performed simultaneously, at the same point intime, or concurrently. Unless otherwise indicated, use of theconjunction “or” as used herein is to be understood as inclusive (any orall of the stated options).

Embodiments of the present disclosure herein describe a method and asystem for recovering a sterilization agent from a waste gaseousmixture. The sterilization agent as described herein may be, forexample, ethylene oxide (ETO). The system may operate at pressure belowand/or at atmospheric pressure and use few moving parts. The energyefficient system may be configured to recover ETO that is clean andreusable while emitting an exhaust with a level of Fro atpart-per-million (ppm) levels.

After the sterilization agent is used for sterilizing items and/orobjects on a closed sealed sterilization chamber, the sterilizationwaste gas pumped out of the sterilization chamber may include a gaseousmixture of inert nitrogen gas, the sterilization agent, such as ethyleneoxide gas, and water vapor. This system leverages the differences in thevapor pressures, and the boiling and freezing points of these threegases in order to separate them. As a result, clean nitrogen gas andliquid water may be safely isolated and disposed of, while the valuableethylene oxide gas may be recollected at high purity, suitable to bereused after appropriate quality testing.

In the embodiments taught herein, the process for recovering asterilization agent from a waste gaseous mixture may be achieved bylowering the gas pressure to a level where the freezing point of the twocomponents are drastically different. The ethylene oxide molecules havesufficient energy to remain in the gas phase but does not covalentlybind to water molecules that are being condensed and cooled from liquidphase, and removing the water from the mixture. In some embodiments, themixture may be further cooled such that the water molecules may befrozen into the solid phase and the solid removed.

The pressure of the dry ethylene oxide gas may be then raised to normalatmospheric pressure so as to elevate its boiling point so as tocondense the ETO into a liquid, which may be removed from the nitrogengas component of the mixture. At the end of the process, pure,uncontaminated ethylene oxide liquid may be collected, ready to beinspected and reused. Clean waste water, sate and free from ethyleneoxide contamination may be collected, tested and then discharged intothe environment, for example. Similarly, the separated nitrogen gas,used in the sterilization process, may be discharged into an abatementsystem or into the atmosphere.

This is a “clean” process where the only waste products are nitrogen gasand water. No absorption materials or metal catalysts are needed, whichwould need to be disposed of periodically. This is also an intrinsicallysafe process the operation in that the waste gas from the sterilizationchamber is maintained at or below atmospheric pressure, so that there isno ethylene oxide gas leakage out from the system. Furthermore, this‘cold’ process may be carried out at near normal sterilizationtemperatures to cryogenic temperatures minimizing the risk ofcatastrophic explosions by staying well below ethylene oxide'sautoignition temperature.

In the context of the present disclosure, two elements that are coupledto in the systems shown herein may refer to elements that may bephysically connected together by tubes and pipes, for example, that maybe thermally isolated to carry refrigerants, hermetic seals forpreventing leaks, pressure valves, flanges, connectors and the like. Theterms used herein such as waste gas, gaseous mixture, waste gaseousmixture, gas streams are all synonymous. They refer to a waste gas thatis a gaseous mixture of chemical components emitted from a sterilizationchamber that is progressively processed to remove, separate and/orpurify the sterilization agent from the waste gas. These terms may referto the original waste gas with all of its chemical components exitingthe sterilization chamber, or the waste gas with any or part of itschemical components removed at any step of the process in recovering thesterilization agent.

FIG. 1 schematically illustrates a block diagram of a first embodimentof a system 10 for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure.System 10 may include a sterilization chamber 1 coupled to a H₂Ocondenser 30 (also known herein as a first condenser) and an ETOcondenser 50 (also known herein as a second condenser). H₂O condenser 30may be coupled to H₂O tank 300 (also known herein as a first tank), andFro condenser 50 may be coupled to ETO tank 500 (also known herein as asecond tank). H₂O tank 300 and ETO tank 500 may be respectively used forstoring the H₂O liquid and ETO during their separation processes fromthe gaseous mixture. The gaseous mixture of waste gas from sterilizationchamber 1 may be pumped into H₂O condenser 30 via a pressure reducingvalve 3 using a chamber evacuation pump 2.

In some embodiments of the present disclosure, pressure reducing valvemay reduce the pressure of the gaseous mixture pumped into H₂O condenser30 to a first predefined value such as 1 psi (e.g., pound per squareinch), for example, or any suitable pressure value, so as to reduce theboiling point temperature of the sterilization agent vapor component inthe waste gas. The system elements operating at a reduced pressure areshown in reduced pressure region 35 (e.g., inside the dotted rectangle).

In some embodiments of the present disclosure, sterilization chamber 1may include an enclosure with the objects and/or items to be sterilized,configured to withstand pressure variances. Sterilization chamber 1 mayinclude inlet and/or outlet ports for removing air, injectingsterilization agent gases, and removing waste gases.

In some embodiments of the present disclosure, chamber evacuation pump 2may include vacuum pumps of various types, capable of removing the wastegas from sterilization chamber 1.

In some embodiments of the present disclosure, system 10 may includepressure reduction valve 3 which may be a throttling valve, capable ofreducing and maintaining system pressure in reduced pressure region 35.

In some embodiments of the present disclosure, H₂O condenser 30 mayinclude a shell-tube, plate or other type of heat exchanger, which maybe cooled by chilled water or refrigerants. H₂O condenser 30 maycondense and trap water vaper and other contaminants, such as oil usedby chamber evacuation pump 2. H₂O condenser 30 may also allow clean ETOgas, together with other inert gases, such as nitrogen (N₂), to passinto ETO condenser 50.

For a pressure of 1 psi, the boding point of water may be reduced to 20deg C., while the boiling point of ETO is 45 deg C. H₂O condenser 30 maybe a heat exchanger that chills the gas mixture to about 4 deg C. tocondense the water vapor and contaminants from the sterilization processof the items and/or objects in sterilization chamber 1 such as oil,polymers formed by the sterilization agent, for example, that may bemixed into the water vapor.

An H₂O discharge valve 301 may be used to discharge H₂O and othercontaminants stored in H₂O tank 300. Similarly, a vacuum release valve302 may be used to release the vacuum inside reduced pressure region 35so as to facilitate the discharge of material such as N₂ from H₂O tank300.

In some embodiments of the present disclosure, the gaseous mixture withthe water vapor removed in reduced pressure region 35 may be pumped intoETO condenser 50 by a separation pump 4 via a separation valve 4A, whichseparates reduced pressure region 35 in system 10 from normal pressureregion 36 in system 10. Separation valve 4A may allow the gaseousmixture with the water vapor removed to enter separation pump 4 whichpumps the gaseous mixture into ETO condenser 50 while raising thepressure of the gaseous mixture to near atmospheric pressure.

In some embodiments of the present disclosure, separation pump 4 mayinclude a vacuum pump capable of maintaining reduced pressures inreduced pressure. region V (e.g., the region shown from pressurereduction valve 3 to separation pump 4). Separation pump 4 may exhaustgases against atmospheric or near atmospheric pressure in a normalpressure region 36 from separation pump 4 to other abatementequipment/atmosphere as shown in FIG. 1. Separation pump 4 may be avacuum pump that is clean by design, namely that the vacuum pump doesnot introduce additional containments into the gaseous mixture.Separation pump 4 may include “dry” vacuum pumps, “oil-less” and“near-oil-less” vacuum pumps, and/or “diaphragm” vacuum pumps.

In some embodiments of the present disclosure, ETO condenser 50 mayinclude a shell-tube, plate or other type of heat exchanger which may becooled by coolant or refrigerant. ETO condenser 50 may condense and trapETO vapors as well as other desirable dilutant such as CO₂, whileallowing non-condensable (Mutant such as nitrogen (N₂), to pass throughto the other abatement equipment atmosphere.

In some embodiments of the present disclosure, ETO condenser 50 maychill the gas mixture to a predefined temperature of about −110 deg C.(e.g., slightly higher than the ETO) melting point temperature of −112deg C.) for condensing the ETO into an ETO vapor. The ETO vapor mayinclude CO₂. ETO tank 500 may be used to store the condensed ETO (andCO₂ mixture, it any) until reuse. An ETO discharge valve 501 may be usedto discharge ETO (and CO₂ mixture, if any) for reuse.

The following embodiments shown in FIGS. 2-6 schematically illustratemodifications to the basic system configuration shown in FIG. 1 forimproving the system energy efficiency and throughput while recovering asterilization agent such as ETO from a waste gaseous mixture outputfront the sterilization chamber.

FIG. 2 schematically illustrates a block diagram of a second embodimentof a system 15 for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure.System 15 may include the same elements of system 10 as shown in FIG. 1.However, the difference between system 10 and system 15 is that system15 may include an H₂O freezer 31 after H₂O condenser 30, and an ETOfreezer 51 after ETO condenser 50. H₂O freezer 31 and/or ETO freezer 51are heat exchangers.

H₂O Freezer 31 may be a shell-tube, plate or other type of heatexchanger, cooled by chilled water, a coolant, or a refrigerant, whichmay further trap residual water vapor in the gaseous mixture that mayhave passed through H₂ O condenser 30 by freezing the molecules to asurface of H₂O Freezer 31. H₂O Freezer 31 may allow clean ETO gas,together with other inert gases, such as nitrogen, to pass through.

Similarly, ETO Freezer 51 may be shell-tube, plate or other types,cooled by a coolant, a compressed refrigerant, or liquid gas typerefrigerant, such as liquid nitrogen, for example, which may furthertrap residual ETO vapor and condensable dilutants such as CO₂ vapors,that have passed through ETO condenser 50 by freezing the molecules to asurface of ETO Freezer 51. ETO Freezer 51 may allow clean nitrogen gasto pass through an atmospheric exhaust valve 6 to the atmosphere.

FIG. 3 schematically illustrates a block diagram of a third embodimentof a system 20 for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure.System 20 may include the same elements of system 15 as shown in FIG. 2.However, the difference between system 15 and system 20 is that betweenseparation pump 4 and ETO condenser 50, system 20 may include an aftercooler 40 coupled to separation pump 4 followed by an exhaust warmer 61and an ETO pre-condenser 50 a coupled to ETO condenser 50. Similarly, anETO freezer economizer 60 may be coupled between ETO) condenser 50 andETO Freezer 51. Exhaust warmer 61 may also be coupled to ETO freezereconomizer 60 and to atmospheric exhaust valve 6.

After cooler 40 may be a heat exchanger that may be used to cool the hotcompressed gas from separation pump 4 using cold water, for example. ETOPre-condenser 50 a may include one or more heat exchangers that may beplaced before and coupled to ETO condenser 50 so as to provideprogressive stages of cooling the gas mixture so as to reduce the heatloading on ETO condenser 50.

ETO Freezer Economizer 60 may be a heat exchanger that pre-cools andpre-freezes the gaseous mixture entering ETO Freezer 51 using coolingenergy from the exhaust gas of ETO Freezer 51.

Exhaust warmer 61 may be a heat exchanger used for pre-cooling andpre-condensing the gaseous mixture entering the ETO pre-condensers usingcooling energy from the exhaust gas of ETO Freezer Economizer 60 andpre-warms the exhaust gas to near ambient temperature before venting thegas to the atmosphere is atmospheric exhaust valve 6.

FIG. 4 schematically illustrates a block diagram of a fourth embodimentof a system 22 for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure.System 22 may include the same elements of system 15 as shown in FIG. 2.However, system 22 may include one or more H₂O freezers and one or moreETO freezers connected in parallel. This may be shown schematically inFIG. 4 as two H₂O freezers 31 and 31′ and ETO Freezers 51 and 51′connected in parallel.

In some embodiments of the present disclosure, one of the H₂O freezers(e.g., H₂O freezer 31) may be performing the freezing operation, whilethe other H₂O freezer (e.g., H₂O freezer 31′) may be thawed out ordefrosted in order to prevent a build-up of solid ice on any one of theH₂O freezer surfaces, Similarly, one of the ETO freezers e.g., ETOfreezer 51) may be performing the freezing operation, while the otherETO freezer (e.g., ETO freezer 51′) may be thawed out in order toprevent a build-up of solid ETO on any one of the H₂O freezer surfaces.

In some embodiments of the present disclosure, control and/or releasevalves may be placed before and/or after each of the two freezers thatmay be placed in parallel which may be used to control which freezer mayroute and cool the gaseous mixture while the other freezer is defrostingor de-thawing. In this manner, the entire process does not need to behalted so as to remove solid water ice and/or solid ETO by using the ETOand/or H₂O parallel freezers.

FIG. 5 schematically illustrates a block diagram of a fifth embodimentof a system 24 for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments oldie present disclosure.System 24 may include all of the elements of systems 20 and 24 shown inthe previous FIGS. 3-4 with additional elements for further improvingthe energy efficiency relative to the previous figures.

The following description uses the system embodiments shown in FIG. 5for providing a summary of the processes highlighting the differentsteps for recovering a sterilization agent from a waste gaseous mixturefrom sterilization chamber 1 in accordance with some embodiments of thepresent disclosure. All or part of these steps described hereinbelow maybe applicable to each of the figures described herein:

-   -   1. The objects and/or items and/or products to be sterilized may        be placed in sterilization chamber 1. A gas mixture including        H₂O vapor, ETO with N₂ (and CO₂, if any) may be introduced into        sterilization chamber 1 through conduits (not shown in FIG. 5)        while pressure reducing valve 3 is in a closed position.    -   2. During the period of sterilizing the objects and/or items        and/or products in sterilization chamber 1, H₂O Condenser 30,        H₂O Freezers 31 and 31′, After Cooler 40, ETO Pre-Condenser 50        a, ETO Condenser 50 and/or ETO Freezers 51 and 51′ may be each        pre-cooled to a predefined temperature.    -   3. H₂O Discharge Valve 301, ETO Discharge Valve 501, and Vacuum        Release Valve 302 may be placed in a closed position. An H₂O        Tank Isolation Valve 303 may be opened while one of H₂O Freezer        Release Valves 31 a or 31′a may be opened while the other        remains closed. Similarly, one of ETO Freezer Release Valves 51        a or 51′a may be opened while the other remains closed.        Atmospheric Exhaust Valve 6 may be opened. Separation Pump 4 may        then be activated causing the pressure inside reduced pressure        region 35 to drop to lower pressure vacuum conditions. Exhaust        in the system 24 may be vented through atmospheric exhaust valve        6 to the atmosphere, which keeps the pressure within the        elements of normal pressure region 36 at or near atmospheric        pressure.    -   4. After sterilization is completed, chamber evacuation pump 2        may be activated, and pressure reducing valve 3 may be opened so        as to allow the waste gas from sterilizing chamber 1 to flow        into H₂O Condenser 30. By varying how much pressure reducing        valve 3 is opened, or by varying the speed of separation pump 4,        or by varying both, the vacuum inside reduced pressure region 35        may be regulated and may be maintained at a predefined pressure,        in some embodiments without the use of H₂O freezers, the        predefined pressure may be in the range of 10 to 0.1 psi. In        other embodiments using H₂O freezers, the predefined pressure        may be in the range of 4 to 0.1 psi.    -   5. At the predefined pressure level, waste gas may flow into H₂O        Condenser 30, which was maintained at a predefined temperature.        Upon contacting the cooling surfaces of H₂O Condenser 30, H₂O        vapor in the stream of the waste gaseous mixture may condense        into liquid form, while the ETO, N₂ and CO₂ molecules in the        gaseous mixture stream of waste gas are not condensed at this        predefined temperature and remain in gaseous form within the        gaseous mixture. Therefore, the condensed H₂O liquid may be        separated from the remaining gases and collected by H₂O Tank        300. Other high boiling point contaminates, such as lubricating        oil mist generated by chamber evacuation pump 2, or polymers        formed hum the ETO, may also be separated from the waste gas        stream by H₂O Condenser 30. These contaminates may also be        collected in H₂O Tank 300.    -   6. The remaining stream of the gaseous mixture may exit from H₂O        condenser 30 into H₂O freezer 31 or 31′, whichever precedes the        opened H₂O Freezer Release Valve 31 a or 31 a′. H₂O Freezers 31        and 31′ have been maintained at predefined temperatures, below        the freezing point of H₂O but above the boiling point of ETO at        a predefined pressure. Upon contacting the cooling surfaces of        Freezer 31 or 31 a, the remaining water vapor in the gas stream        may freeze on these cooling surfaces, further reducing the        amount of water vapor in the gaseous mixture.    -   7. Whenever the cooling surfaces of either H₂O Freezer 31 and        31′ accumulate too much solid H₂O, and the thickness of the ice        is thick enough in one of the freezers so as to inhibit proper        heat transfer and efficient H₂O removal from the gas stream        (e.g., the gaseous mixture), then freezer release valve 31 a or        31 a′ of the inefficient freezer may be closed while the other        Freezer Release Valve remains opened.    -   8. As the gas stream is routed to the other H₂O Freezer, H₂O        removal from the gas stream may continue inside the        still-operating efficient freezer. Cooling inside the        inefficient freezer with too much ice build-up may be turned        off, while defrosting heaters on or near the cooling surfaces        may be turned on, so a to melt the solid ice that has built up        on the cooling surfaces of the inefficient Freezer back into        liquid form. In other embodiments, warm fluid may be pumped into        warm the cooling surfaces. This liquid, mainly water, may flow        into and be further collected by H₂O Tank 300 via H₂O Tank        isolation Valve 303. When the ice-melting and defrosting mock of        the inefficiently-operating freezer has been completed, (e.g.,        its cooling surfaces cleared of ice built-up), the defrosting        heaters may be turned off and cooling may resume to cool the        Freezer back to its predefined temperature. When the other        Freezer has accumulated too much ice built-up, the same        ice-removal steps can be repeated to defrost ice from its        cooling surfaces. In this manner, efficient H₂O removal from the        gas stream may be maintained without having to stop the entire        process in system 24 for ice-removal in the cooling elements.    -   9. Whenever H₂O Tank 300 is full, H₂O tank isolation valve 303        may be closed and vacuum release valve 302 may be opened to        allow the pressure inside the H₂O Tank 300 to return atmospheric        pressure. After that, H₂O Discharge Valve 301 may be opened to        discharge the contents of H₂O Tank 300. After discharge, valves        301 and 302 may be closed, and valve 303 may be opened. H₂O Tank        300 may then continue to receive condensate from H₂O Condenser        30 and H₂O Freezers 31 and 31′. In this manner, H₂O Tank 300 may        be discharged completely while waste gas removal from        Sterilization Chamber 1 may continue without interruption.    -   10. The remaining stream of waste gas mixture now free of H₂O        vapor may exit from H₂O Freezers 31 and 31′. The remaining        stream of waste gas mixture may include ETO vapor, N₂ and CO₂        gas, and pass through corresponding H₂O Freezer Release Valve 31        a or 31 a′, to separation pump 4 for compression to atmospheric        or near-atmospheric pressure.    -   11. The compression process by separation pump 4 increases the        gas stream temperature to above room temperature. The hot gas        stream may then enter ETO After Cooler 40, a heat exchanger        cooled by regular cooling water may be used to cool the gaseous        mixture to near room temperature.    -   12. After being cooled by ETO After Cooler 40, the near-room        temperature gas stream may enter an Exhaust Warmer 61. Exhaust        Warmer 61 may be a heat exchanger that warms the final cold        exhaust gas (e.g., after ETO removal) to near-room, temperature        before being released into the atmosphere. It may also be used        to recover expensive cooling energy from that cold exhaust gas,        to pre-cool the gas stream, and to pre-condense some of the ETO        vapor inside the gas stream. This conserved energy may be used        to cool ETO Pre-Condenser 50 a.        -   Since the freezing point of ETO is extremely low (−112            degrees C.), ETO Condenser 50 is cooled to extremely low            temperatures. In order to reduce heat load to ETO Condenser            so (e.g., increase cooling efficiency), and to provide more            effective condensing of the ETO vapor in the gaseous            mixture. ETO Pre-Condenser 50 a was placed before ETO            Condenser 50 as shown in FIG. 5, which is not by way of            limitation of the embodiments of the present disclosure. One            or more pre-condensers may be placed in series before ETO            Condenser 50. ETO Pre-Condensers may each pre-cooled to            respective predefined temperatures such that each            Pre-Condenser may be progressively colder (e.g., at lower            temperatures) as they are positioned closer to ETO Condenser            50, with ETO Condenser 50 being the coldest (e.g., at the            lowest temperature).        -   As the gas stream exits. from Exhaust Warmer 61 and enters            ETO Pre-Condenser 50 a, the gas stream may be pre-cooled and            the ETO vapors may be pre-condensed passing through the ETO            Pre-Condenser 50 a. Similarly, if a series of ETO            Pre-Condensers may be placed before ETO Condenser 50, the            gas stream may be progressively cooled, with ETO vapors            progressively condensed as the gas stream passes through            each of ETO Pre-Condensers in series. By pre-cooling the gas            stream in one single stage, or progressively pre-cooling the            gas stream in multiple stages of progressively colder            temperatures, the cooling system using Pre-Condensers is a            more energy efficient cooling system to cool the ETO            extremely low temperatures by using a series of            Pre-Condensers so as to stagger the temperatures to            progressively lower temperatures, yet higher than the            temperature of the final ETO Condenser 50. Thus, the total            energy needed to cool the gas stream was reduced, while            still cooling the gas stream, to the same low temperature.    -   13. ETO Condenser 50 may be pre-cooled and maintained at a        predefined temperature as the gas stream enters ETO Condenser        50. Inside ETO Condenser 50, ETO vapor may be condensed into        liquid form and was separated from the stream of the gaseous        mixture. The ETO then be collected by ETO Tank 500.        -   Note that if CO₂ gas is present in the remaining gas stream            from, separation pump 4, it will also be frozen into solid            form on the cooling surfaces of ETO Pre-Condenser 50 a and            ETO Condenser 50. CO₂ gas may be dissolved in the ETO liquid            condensate and collected in ETO Tank 500. However, N₂ gas in            the gas mixture will not be condensed nor frozen at the            predefined temperatures of ETO Pre-Condenser 51′ or ETO            Condenser 50. Therefore, N₂ gas may be separated from the            ETO condensate and CO₂ ice.    -   14. After condensable ETO vapor was removed from the gas stream        by ETO Pre-Condensers 50 a and ETO Condenser 50, the gas stream        may enter ETO Freezer Economizer 60 or 60′, whichever had a        corresponding ETO Freezer Release Valve 51 a or 51 a′ opened.        ETO Freezer Economizer 60 and 60′ may be a heat exchanger that        utilizes the cooling energy from the cold exhaust of ETO        Freezers 51 and 51′ to pre-cool the gas stream before entering        ETO) Freezers 51 and 51′.    -   15. ETO Freezer 51 and 51′ may be pre-cooled to a predefined        temperature (e.g., in a range of −112 deg C. to −196 deg C.),        below the freezing point of ETO) and above the boiling point of        N₂. After the gas stream enters ETO Freezers 51 and 51′, the        remaining ETO vapor in the gas stream may freeze onto the        cooling surfaces of the ETO Freezers where the ETO may be        separated from the gas stream. Consequently, ETO content in the        gas stream may be reduced to a minimum level.    -   16. The gas stream exiting ETO Freezers 51 and 51′ may include        N₂ gas free of environmentally harmful ETD (e.g., reduced to        sub-ppm levels of ETO). With all of the contaminates removed        from the gaseous mixture, the remaining clean gas is extremely        cold. and the valuable cooling energy of the N₂ gas may be        recovered in system 24.        -   The cold N₂ gas exiting ETO Freezers 51 and 51′ may be            coupled into corresponding ETO Freezer Economizers 60 and            60″, which are heat exchangers. The cold N₂ gas from ETO            Freezers 51 and 51′may be used as a cooling medium that may            be fed back to cool ETO Freezer Economizers 60 and 60′,            which may subsequently be used to cool the gas stream            entering the inlets of ETO Freezers 51 and 51′.    -   17. Since the temperature of the N₂ gas is below the freezing        point of ETO, ETO Freezer Economizers 60 and 60′ may have solid        ETO frozen onto the cooling surfaces of the Economizer. Whenever        the cooling surfaces of either ETO Freezer Economizer 60 and ETO        Freezer 51, or ETO Freezer Economizer 60′ and ETO Freezer 51′        cooling surfaces may accumulate too much solid ETO, such that        the thickness of the solid ETO may inhibit proper heat transfer        and efficient ETO removal from the gas stream, then the        corresponding ETO Freezer Release Valve 51 a or 51 a′ may be        closed while the other ETO Freezer Release Valve remains open.        As the gas stream may be routed to the other ETO Freezer        Economizer and ETO Freezer, ETO removal from the gas stream may        continue.        -   Cooling may be turned off in the ETO Economizer and ETO            Freezer with too much solid ETO build-up, and heating            applied to the cooling surfaces was turned on. The solid ETO            that accumulated on the cooling surfaces of the ETO            Economizer and ETO Freezer may be defrosted back into ETO            liquid which may be collected by ETO Tank 500. In other            embodiments, warm fluid may be pumped into warm the cooling            surfaces. When ETO Economizer and ETO Freezer have been            completed defrosted, heating may then be turned off and the            cooling process restored, so as to cool the ETO Freezer back            to its predefined temperature. Similarly, when the other ETO            Freezer has accumulated too much. ETO solid built-up, the            same solid ETO removal steps may be repeated to clean the            cooling surfaces.    -   18. The cold N₂ gas stream passing through ETO Freezer        Economizer 60 or 60′ may be used to transfer its cooling energy        to other cooling elements in the system. For example, it may be        passed though the corresponding ETO Freezer Release Valve 51 a/        51 ′a. This cold N₂ gas may be routed to Exhaust Warmer 61, so        as to pre-cool the gas stream that was about to enter ETO        Pre-Condensers 50 a. This process may warm the clean N₂ gas to        near room temperature as the N₂ gas cools the gas stream.        Therefore, reducing the amount of energy needed to cool the ETO        Pre-Condensers.    -   19. Whenever the contents of ETO Tank 500 may be discharged, ETO        discharge valve 501 may be opened. Since the pressure inside ETO        Tank 500 may be at or near atmospheric pressure, pure ETO stored        inside ETO Tank 500 may flow out without interrupting gas        removal from Sterilization Chamber 1.    -   20. After removal of the waste gas from Sterilization Chamber 1        is completed, Pressuring Reducing Valve 3 and Freezer Release        Valves 31 a and 31 ′a may be closed. Chamber Evacuation Pump 2        and Separation Pump 4 may be turned off.    -   21. In reduced pressure region 35, after ice may be removed from        H₂O Freezers 31 and 31′, and all condensates collected in H₂O        Tank 300, valve 303 may be closed and Vacuum Release Valve 302        may be opened so as to break the vacuum equalizing the pressure        inside H₂O Tank 300 with atmospheric pressure. H₂O Discharge        Valve 301 may be opened to allow the contents of H₂O Tank 300 to        flow freely from the tank. The discharged contents from H₂O Tank        300 may include clean water with slight oil mists from Chamber        Evacuation Pump 2 and traces of ETO polymers. This water may be        easily filtered and disposed of.    -   22. In normal pressure region 36, after Chamber Evacuation Pump        2 and Separation Pump 4 are turned off, ETO Freezer Release        Valve 51 a and 51 ′a may be closed to prevent ETO vapor to        escape into the atmosphere during ETO solid melting process in        all of the cooling elements. Then, cooling of ETO Freezers 51        and 51′ may be turned off and heating of the ETO Freezers 51 and        51′ and ETO Freezer In other embodiments, warm fluid may be        pumped into warm the cooling surfaces. Economizers 60 and 60′        may be turned on. Solid ETO that collected on surfaces of ETO        Freezers 51 and 51′, and ETO Freezer Economizers 60 and 60′ may        melt back into liquid ETO, which may be collected by ETO Tank        500 for reuse.    -   23. After inching of solid ETO has been completed, heating of        the ETO Freezers 51 and 51′ and ETO Freezer Economizers 60 and        60′ may be turned off, ETO Discharge Valve 501 may be opened to        allow the contents of ETO Tank 500 to be discharge for re-use.        Since the pressure inside normal pressure region 36 may be at or        near atmospheric pressure, the contents of ETO Tank 500 may flow        freely from ETO Tank 500, the contents of Tank 500 may include        pure ETO, free of water and other contaminates. In some cases,        the content may be a mixture of ETO and CO₂ if that was the        mixture used in Sterilization Chamber 1. This mixture is also        clean and free from water and other contaminates. The pure ETO,        or clean ETO/CO₂ mixture, after being discharged from Tank 500,        may be re-used in future processes.

The process for recovering and/or purifying a sterilization agent from awaste gas mixture as described hereinabove is not be way of limitationof the embodiments of the present disclosure. All or any steps of thisprocess may be used in an of the FIGS. 1-6 shown herein in any suitablecombination or order. The sterilization agent is not limited herein toETO but may include other sterilization agents such as propylene oxide.for example.

FIG. 6 schematically illustrates a block diagram of a sixth embodimentof a system 26 for recovering a sterilization agent from a waste gaseousmixture, in accordance with some embodiments of the present disclosure.System 26 may include elements of system 15. However, the waste gaseousmixture processed by system 26 may be the waste gas from one or moresterilization chambers, denoted sterilization chamber 1. sterilizationchamber 1′, and sterilization chamber 1″. Each of the one or moresterilization chambers may include respective one or more evacuationpumps denoted chamber evacuation pump chamber evacuation pump 2′, andchamber evacuation pump 2″ and one or more respective chamber waste gasexhaust valves denoted chamber waste gas exhaust valve 7, chamber wastegas exhaust valve 7′, and chamber waste gas exhaust valve 7″.

The waste gas from each of the one or more sterilization chambers maypass into a waste holding tank 700 and then coupled into the reducepressure region 35 via pressure reducing valve 3 and normal pressureregion 36 for recovering the ETO sterilization agent from the waste gasfrom the one or more sterilization chambers. Stated differently, thewaste gases from the multiple sterilization chambers may be processed bya single sterilization agent recovery/process system as shown in FIG. 6.Waste holding tank 700 may be of a variable volume so that pressure inthe tank may be kept at atmospheric pressure, or a fixed volume type oftank.

FIG. 7 is a flowchart depicting a method 400 for recovering, asterilization agent from a waste gaseous mixture, in accordance withsome embodiments of the present disclosure.

Method 400 may include receiving 405 a waste gas from a sterilizationchamber. The waste gas may include a gaseous mixture of a sterilizationagent, nitrogen gas, and water vapor.

Method 400 may include reducing 410 a pressure of the gaseous mixture toa first predefined pressure so as to reduce a boiling point temperatureof the sterilization agent to below a freezing point temperature of thewater vapor in the gaseous mixture.

Method 400 may include cooling 415 the gaseous .mixture with thepressure at the first predefined pressure to a temperature below aboiling point temperature and above the freezing point temperature ofthe water vapor, and removing condensed water vapor from the gaseousmixture.

Method 400 may include raising 420 the pressure of the gaseous mixtureto a second predefined pressure greater than the first predefinedpressure so as to elevate a boiling point temperature of thesterilization agent in the gaseous mixture.

Method 400 may include cooling 425 the gaseous mixture at the secondpredefined pressure to a temperature below the boiling point temperatureand above a freezing point temperature of the sterilization agentcausing the sterilization agent to condense into a liquid.

Method 400 may include separating 430 the liquid sterilization agentfrom the gaseous mixture so as to recover the sterilization agent forreuse from the waste gas.

Method 400 may include discharging 435 the nitrogen gas remaining in thegaseous mixture to the atmosphere or collecting the nitrogen gas forreuse.

In some embodiments of the present disclosure, a system for recovering asterilization agent from a waste gaseous mixture may include a pressurereducing valve for reducing a pressure of a waste gas from one or moresterilization chambers to a first predefined pressure. The waste gas mayinclude a gaseous mixture of a sterilization agent, nitrogen gas, andwater vapor. A first condenser may be configured to receive the gaseousmixture via the pressure reducing valve, and to cool the gaseous mixtureto a temperature below a boiling point temperature and above a freezingpoint temperature of the water vapor at the first predefined pressure. Afirst tank, coupled to the first condenser, may store the condensedwater vapor separated from the gaseous mixture in the first condenser. Aseparation pump coupled to the first tank may raise the pressure of thegaseous mixture to a second predefined pressure. A second condenser maybe configured to receive the gaseous mixture from the separation pump,to cool the gaseous mixture to a temperature below a boiling pointtemperature and above a freezing point temperature of the sterilizationagent at the second predefined pressure causing the sterilization agentto condense into a liquid, and to discharge the nitrogen gas remainingin the gaseous mixture. A second tank, coupled to the second condenser,may store the sterilization agent separated from the gaseous mixture inthe second condenser.

In some embodiments of the present disclosure, the sterilization agentmay include ethylene oxide (ETO).

In some embodiments of the present disclosure, the first predefinedpressure may be 1 pound per square inch and the second predefinedpressure is atmospheric pressure.

In some embodiments of the present disclosure, the boiling pointtemperature of the water vapor may be 20 deg C. when the pressure of thegaseous mixture is 1 psi.

In some embodiments of the present disclosure, boiling point temperatureof the ETO may be 10 deg C. when the pressure of the gaseous mixture isatmospheric pressure.

In some embodiments of the present disclosure, the sterilization agentmay be propylene oxide.

In some embodiments of the present disclosure, the system may include achamber evacuation pump coupled to the pressure reducing valve forpumping the waste gas into the first condenser.

In some embodiments of the present disclosure, the system may include anexhaust warmer and a freezer economizer for recovering cooling energy inthe system.

In some embodiments of the present disclosure, the system may includeone or more H₂O freezers coupled to the first condenser and theseparation pump, and wherein each of the one or more H₂O freezers mayfreeze H₂O molecules in the water vapor to a freezer surface.

In some embodiments of the present disclosure, at least two H₂O freezersfrom the one or more H₂O freezers may be connected in parallel coupledbetween the first condenser and the separation pump.

In some embodiments of the present disclosure, the system may include anETO freezer coupled to the second condenser for trapping residual vaporsof the sterilization agent.

In some embodiments of the present disclosure, the system may include awaste gas holding tank coupled to the pressure reducing valve and to theone or more sterilization chambers for collecting the waste gas from theone or more sterilization chambers.

In some embodiments of the present disclosure, the system may includeone or more ETO pre-condensers placed in series before the secondcondenser, wherein each of the one or more pre-condensers may haveprogressively lower temperatures above the temperature of the secondcondenser.

In some embodiments of the present disclosure, a method for recovering asterilization agent from a waste gaseous mixture may include receiving,a waste gas from a sterilization chamber. The waste gas may include agaseous mixture of a sterilization agent, nitrogen gas, and water vapor,A pressure of the gaseous mixture may be reduced to a first predefinedpressure so as to reduce a boiling point temperature of thesterilization agent to below the freezing point temperature of the watervapor in the gaseous mixture. The gaseous mixture with the pressure atthe first predefined pressure may be cooled to a temperature below aboiling point temperature and above the freezing point temperature ofthe water vapor. Condensed water vapor may be removed from the gaseousmixture. The pressure of the gaseous mixture may be raised to a secondpredefined pressure greater than the first predefined pressure so as toelevate a boiling point temperature of the sterilization agent in thegaseous mixture. The gaseous mixture at the second predefined pressuremay be cooled to a temperature below the boiling point temperature andabove a freezing point temperature of the sterilization agent causingthe sterilization agent to condense into a liquid. The liquidsterilization agent may be separated from the gaseous mixture so as torecover the sterilization agent for reuse from the waste gas. Thenitrogen gas remaining in the gaseous mixture may be discharged.

In some embodiments of the present disclosure, the, sterilization agentmay include ethylene oxide (ETO).

In some embodiments of the present disclosure, the first predefinedpressure may be 1 pound per square inch (psi) and the second predefinedpressure may be atmospheric pressure.

In some embodiments of the present disclosure, the boiling pointtemperature of the water vapor may be 20 deg C. when the pressure of thegaseous mixture is 1 psi,

In some embodiments of the present disclosure, the boiling pointtemperature of the ETO may be 10 deg C. when the pressure of the gaseousmixture is atmospheric pressure.

In some embodiments of the present disclosure, the sterilization agentmay be propylene oxide (PO).

In some embodiments of the present disclosure, discharging the nitrogengas may include discharging the nitrogen gas to the atmosphere orcollecting the discharged nitrogen gas for reuse.

In some embodiments of the present disclosure, the method may includerecovering cooling energy in the system by using an exhaust warmer and afreezer economizer.

In some embodiments of the present disclosure, the method may includefreezing H₂O molecules in the water vapor to a freezer surface of one ormore H₂O freezers.

In some embodiments of the present disclosure, at least two H₂O freezersfrom the one or more H₂O freezers may be connected in parallel, and themethod may include defrosting at least one of the H₂O freezers horn theat least two parallel H2O freezers.

In some embodiments of the present disclosure, the method may includetrapping residual vapors of the sterilization agent using one or moreETO freezers coupled to the second condenser

In some embodiments of the present disclosure, at least two ETO freezersfrom the one or more H₂O freezers may be connected in parallel, and themethod may include defrosting at least one of the ETO freezers from theat least two parallel ETO freezers.

In some embodiments of the present disclosure, the method may includecollecting the waste gas from the one or more sterilization chambers ina waste gas holding tank.

In some embodiments of the present disclosure, the method may includesetting the temperatures of each of one or more ETO pre-condensersplaced in series before the second condenser to progressively lowertemperatures above the temperature of the second condenser.

In case there is more than one sterilization chambers that exhaust wastegas, thereby creating a large stream waste gas flow, an increase in thesize of each of the elements of a sterilization agent recovering systemand thereby an increase in the size of the entire sterilization agentrecovering system would typically be required.

A size increase of the recovering system would incur an increase in thespace occupied by the system, which is usually already restricted, aswell as an increase in installation and operation costs.

The cost of operation is increased to handle an increased waste gas flowcoming from more than one sterilization chambers, especially due to thecost of cooling required to cool the condensers, and especially forcooling the condensers and the freezer(s), if such freezer(s) are at allimplemented in the system.

The increase in cost of cooling is due to the increased amount ofgaseous sterilizing agent in the waste gas stream, but also due to theincreased amount of dilution gas(es), e.g., N₂ and possibly CO₂, whichare present in the waste gas stream.

The problem of increased cooling energy is even worsened by the factthat, in cooling systems, the cost of cooling drastically increases asthe intended temperature decreases. For example, in one embodiment, oneof the condensers may be cooled as low as minus 110 degrees Celsius. Thecost to cool the condenser to this low temperature costs about ten timesmore than it is to cool another condenser of the system, which operatesat about 4 degrees Celsius.

Accordingly, the present disclosure provides a recovering system thatincludes a gas separator and in some embodiments a gas evaporator. A gasseparator and possibly a gas evaporator are introduced after the exhaustpumps of one or more sterilization chambers and before the pressurereducing valve of the system for recovering a sterilization agent, whichis schematically illustrated in FIG. 1.

FIG. 8 schematically illustrates a block diagram of an embodiment of asystem 80 for recovering a sterilization agent from a waste gaseousmixture from one or more sterilization chambers, in accordance with someembodiments of the present disclosure.

System 80 may include one or more sterilization chambers 1 each coupledto a H₂O tank 300 (also known herein as a first tank), a H₂O condenser30 (also known herein as a first condenser) and an ETO condenser 50(also known herein as a second condenser). H₂O condenser 30 may becoupled to H₂O tank 300, and ETO condenser 50 may be coupled to ETO tank500 (also known herein as a second tank). H₂O tank 300 and ETO tank 500may be respectively used for storing the H₂O liquid and ETO duringand/or after their separation process. In some embodiments, the gaseousmixture of waste gas from one or more sterilization chambers 1 may bepumped into gas separator 82 using a chamber evacuation pump 2.

Thus, system 80, unlike system 10 is designed such that the waste gasmixture from the one or more sterilization chambers 1 first enters H₂Otank 300, while H₂O condenser 30 that is coupled to H₂O tank 300 is onlyreached after passage through H₂O tank 300.

In addition, system 80 farther comprises a gas separator 82, coupled tothe one or more sterilization chambers 1, e.g., via evacuation pump 2,and further coupled to H₂O tank 300, via pressure reducing valve 3.

In some embodiments, gas separator 82 may contain common water. The gasseparator 82 may be configured to wash waste gas from one or moresterilization chambers 1, with water. As the waste gas comprises agaseous mixture of a sterilization agent, nitrogen gas, and water vapor,the sterilization agent and water vapor may be absorbed by the waterwithin gas separator 82, thereby creating a water-gaseous sterilizationagent mixture that may be collected at a bottom section of gas separator82, and the dilution gas, e.g., N₂ gas may be exhausted at a top sectionof gas separator 82.

Gas separator 82 may receive a large waste gas stream flow exhaustingfrom the one or more sterilization chambers 1 via exhaust pumps, and mayretain the waste as stream inside gas separator 82 for a period of time0.1 to 10 minutes to increase the surface area which the waste gas comesin contact with the water contained in the gas separator 82. This allowswater soluble and condensable components in the waste gas stream, inparticular the gaseous sterilizing agent and water vapors, to bedissolved and condensed into the water, forming a water mixture that isrich in sterilization agent, i.e., a water-gaseous sterilization agentmixture. The water-gaseous sterilization agent mixture may then becollected at the bottom portion of the gas separator 82 or in adesignated water mixture receiving tank (not shown). At the same time,the non-water soluble and non-condensable components in the waste gasstream, in particular the insert dilution gas(es), e.g., N₂ gas andpossibly CO₂ gas, may be separated from the water-gaseous sterilizationagent mixture, and may exit near the top section of the gas separator82, and may then be exhausted into the atmosphere or to other abatementequipment.

According to some embodiments, gas separator 82 in elect separates thegaseous sterilization agent, e.g., ethylene oxide (ETO) or propyleneoxide (PO) from the inert dilution gas(es), e.g., N₂ gas, CO₂ gas, or acombination of N₂ gas and CO₂ gas, by taking advantage of thedifferences in their solubility property in water. The gaseoussterilization agents are highly soluble in water, i.e., 100 grams ETOdissolve in 1 liter of water, and 400 g. PO dissolve in 1 liter of waterat 20 degrees Celsius, while inert dilution gases are considered notsoluble in water, as only 0.02g of N₂dissolve in 1 liter of water, andonly 1.7 g of CO₂ dissolve in 1 liter of water, at the same temperatureof 20 degrees Celsius. By retaining and interfacing the waste gas streamwith water, the gas separator 82 may dissolve the sterilization agentfrom the waste gas stream into the water. That is, the clean water ingas separator 82 effectively wash the gas stream to thereby strip thewaste gas stream of the sterilization agent and only leave cleandilution gas as part of the waste gas stream. The dilution gas, e.g., N₂and possibly CO₂, may then be exhausted into the atmosphere or otherabatement equipment through a top portion of gas separator 82, while thewater-gaseous sterilization agent mixture may exit gas separator 82through its bottom portion.

According to some embodiments, since system 80 exhausts the dilutiongas, e.g., N₂ and possibly CO₂ gas at an early stage of the recoveringprocess, i.e., the dilution gas exits system 80 from gas separator 82,system 80 need to treat the dilution gas throughout the entire system,as done, for example, in system 10. This early exhaustion of thedilution gas from the system leads to recovering system 80 being smallercompared to the basic recovering system 10 thereby system 80 consumesless space, and possibly less energy as the entire procedure is simpler,which are both important advantages of system 80.

In some embodiments, the recovering system may be even smaller, sincethe sterilization agent dissolved in water, i.e., the water-gaseoussterilization agent mixture, may be stored to be processed later by arecovering system. Thus, the one or more sterilization chambers 1, oneor more evacuation pumps 2 and the gas separator 82 along with awater-gaseous sterilization agent mixture container, may be part of aninitial separation system, which separates the dilution gas from thewaste gas thereby leaving the sterilization agent dissolved in water,while the water-gaseous sterilization agent mixture may later beinputted into a recovering system, which is thus smaller than system 80.

In some embodiments, the water-gaseous sterilization agent mixture fromthe gas separator 82 can be stored at the lower part of the gasseparator 82, stored in separate designated tanks, or may be directlyconnected to H₂O tank 300.

In some embodiments of the present disclosure, pressure reducing valve 3may reduce the pressure of the water-gaseous sterilization agent mixturepumped into H₂O tank 300 to a first predefined value such as 1 psi(e.g., pound per square inch), for example, or any suitable pressurevalue, so as to reduce the boiling point temperature of thesterilization agent component in the water-gaseous sterilization agentmixture. The system elements operating at a reduced pressure are shownin reduced pressure region 35 (e.g., inside the dotted rectangle).

In some embodiments of the present disclosure, one or more sterilizationchambers 1 may include an enclosure with the objects and/or items to besterilized, configured to withstand pressure variances. One or moresterilization chambers 1 may include inlet and/or outlet ports forremoving air, injecting sterilization agent gases, and removing wastegases.

In some embodiments of the present disclosure, chamber evacuation pump 2may comprise vacuum pumps of various types, capable of removing thewaste gas from one or more sterilization chambers 1. In someembodiments, when there is more than one sterilization chambers 1, eachsterilization chamber may be coupled to a corresponding chamberevacuation pump 2.

In some embodiments of the present disclosure, system 80 may includepressure reduction valve 3 which may be a throttling valve, capable ofreducing and maintaining system pressure in reduced pressure region 35.

In some embodiments, H₂O tank 300 may be heated to heat thewater-gaseous sterilization agent mixture to a temperature aboveboiling, point temperature of the sterilization agent and above afreezing point temperature of the water to produce gaseous sterilizationagent and water vapor.

In some embodiments of the present disclosure, H₂O condenser 30 mayinclude a shell-tube, plate or other type of heat exchanger, which maybe cooled by chilled water or refrigerants. H₂O condenser 30 maycondense and trap water vapor and other contaminants, such as oil usedby chamber evacuation pump 2. H₂O condenser 30 may also allow the cleangaseous sterilization agent to pass into ETO condenser 50.

The condensed water vapor may be received by H₂O tank 300, while H₂Otank 300 keeps on heating the water-gaseous sterilization agent mixtureto maintain the process of separating the sterilization agent from thewater vapor. The water-gaseous sterilization agent mixture iscontinuously heated by H₂O tank 300, which also collects condensed watervapor that is condensed by H₂O condenser 30, and gaseous sterilizationagent is passed from H₂O condenser 30 to ETO condenser 50, until theentire amount of gaseous sterilization agent is passed into ETOcondenser 50. The process of heating H₂O tank 300 is repeated until theentire amount of gaseous sterilization agent is removed from H₂O tank300 into ETO condenser 50.

For example, assuming the percentage of dissolved water vapor in thewater gaseous sterilization agent mixture is 50%, and the percentage ofthe dissolved gaseous sterilization agent is 50%, after H₂O tank 300 isheated to produce water vapor and some gaseous sterilization agent, thewater vapor and gaseous sterilization agent enter H₂O condenser 30, inwhich water vapor is condensed and goes back into H₂O tank 300. Duringthat same process, the gaseous sterilization agent is moved from H₂Ocondenser 30 to ETO condenser 50. Now, the water-gaseous sterilizationagent mixture in H₂O tank 300 comprises 60% water and 40% gaseoussterilization agent since some of the sterilization agent has moved toETO condenser 50. This new mixture is reheated within H₂O tank 300, toproduce water vapor to be condensed by H₂O condenser 30, and somegaseous sterilization agent to be moved into ETO condenser 50, therebyreducing the percentage of the sterilization agent within H₂O tank 300once again. This process repeats itself until H₂O tank 300 contains onlywater, while the entire amount of gaseous sterilization agent is presentin ETO condenser 50.

In some embodiments, the ETO evaporation process performed by H₂O tank300, comes to an end when the boiling temperature of the mixture withinH₂O tank 300 starts to increase, e.g., from the boiling temperature ofETU it increases to the boiling temperature of water.

For a pressure of 1 psi, the boiling point of water may be reduced to 20deg C., while the boiling, point of ETO is −45 deg C. H₂O condenser 30may be a heat exchanger that chills the gas mixture to about 4 deg C. tocondense the water vapor and contaminants from the sterilization processof the items and or objects in one or more sterilization chambers 1 suchas oil, polymers formed by the sterilization agent, for example, thatmay be mixed into the water vapor.

An H₂O discharge valve 301 may be used to discharge H₂O and othercontaminants stored in H₂O tank 300. A vacuum release valve 302 may beused to release the vacuum inside reduced pressure region 35 so as toallow the pressure inside H₂O tank 300 to equalize with the pressureoutside of valve 301, so that the content of H₂O tank 300 can bedischarged via gravity.

In some embodiments of the present disclosure, the gaseous sterilizationagent with the water vapor removed in reduced pressure region 35, may bepumped into ETO condenser 50 by a separation pump 4 via a separationvalve 4A, which separates reduced pressure region 35 in system 80 fromnormal pressure region 36 in system 80. Separation valve 4A may allowthe gaseous sterilization agent to enter separation pump 4 which pumpsthe gaseous sterilization agent into ETO condenser 50 while raising thepressure of the gaseous sterilization agent to near atmosphericpressure.

In some embodiments of the present disclosure, separation pump 4 mayinclude a vacuum pump capable of maintaining reduced pressures inreduced pressure region 35 (e.g., the region shown from pressurereduction valve 3 to separation pump 4). Separation pump 4 may exhaustgases against atmospheric or near atmospheric pressure in a normalpressure region 36 from separation pump 4 to other abatementequipment/atmosphere as shown in FIG. 8. Separation pump 4 may be avacuum pump that is clean by design, namely that the vacuum pump doesnot introduce additional containments into the gaseous sterilizationagent. Separation pump 4 may include “dry” vacuum pumps, “oil-less” and“near-oil-less” vacuum pumps, and/or “diaphragm” an pumps.

In some embodiments of the present disclosure, ETO condenser 50 mayinclude a shell-tube, plate or other type of heat exchanger which may becooled by coolant or refrigerant. ETO condenser 50 may condense and trapsterilization agent vapors e.g., ETO vapors.

In some embodiments of the present disclosure, ETO condenser 50 maychill the gaseous sterilization agent to a predefined temperature ofabout −110 deg C. slightly higher than the ETO melting point temperatureof −112 deg C.) for condensing the ETO into an ETO liquid. The ETO vapormay include CO₂. ETO tank 500 may be used to store the condensed ETO(and CO₂ mixture if any) until reuse. An ETO discharge valve 501 may beused to discharge ETO (and CO₂ mixture, if any) for reuse.

In some embodiments, the water in gas separator 82 may be replaced byEthylene Glycol, or a mixture of water and Ethylene Glycol. In someembodiments, gas separator 82 may be cooled to cool the water, EthyleneGlycol, or water/Ethylene Glycol mixture to between 10 to −40 deg C., sothat condensation and solubility of the sterilization agent, ETO, in thewater, Ethylene Glycol or water/Ethylene Glycol mixture is furtherimproved.

For typical sterilization chambers, the time it takes a sterilizationchamber to exhaust ETO gas is between 15-30 minutes, while the wholesterilization cycle takes about 8-12 hours. For a system without the gasseparator, the system's entire components need to be sized (e.g.,enlarged) such to treat all of the exhaust waste stream from more thanone sterilization chambers. However, for a system comprising a gasseparator, the entire waste gas stream may be treated within 15-30minutes by the large gas separator via washing the waste gas with water,separating the gaseous sterilization agent from the inert dilution gasesand storing the gaseous sterilization agent in a liquid form ofwater-gaseous sterilization agent mixture. Thus, the rest of therecovering system can be smaller, compared to a recovering system withno gas separator, due to having all 8-12 hours of the sterilizationcycle time to treat and separate ETO from the water-gaseoussterilization agent mixture.

FIG. 9 schematically illustrates a block diagram of an embodiment of asystem for recovering a sterilization agent from a waste gaseous mixturefrom one or more sterilization chambers, in accordance with someembodiments of the present disclosure.

According to some embodiments, system 90 may differ from system 80 inthat system 90 may further comprise an evaporator 92, which may be thecomponent of system 90 designated to heat the water-gaseoussterilization agent mixture instead of H₂O tank 300 as in system 80. Byhaving a designated component within system 90, that is configured toheat the water-gaseous sterilization agent mixture prior to separationof the water vapor from the sterilization agent, the energy of isincreased, as there is no need for continuously reheating the mixture ofwater and sterilization agent within H₂O tank 300, until thesterilization agent is entirely separated from the condensed water thatis continuously received by H₂O tank 300.

System 90 may include one or mote sterilization chambers 1 each coupledto a H₂O condenser 30 (also known herein as a first condenser), a H₂Otank 300 (also known herein as a first tank), and an ETO condenser 50(also known herein as a second condenser). H₂O condenser 30 may becoupled to H₂O tank 300, and ETO condenser 50 may be coupled to ETO tank500 (also known herein as a second tank), H₂O tank 300 and ETO tank 500may be respectively used for storing the H₂O liquid and ETO duringand/or after their separation process.

System 90 further comprises a gas separator 82, coupled to the one ormore sterilization chambers 1, e.g., via evacuation pump 2, and furthercoupled to evaporator 92, e.g., via pressure reducing valve 3. In someembodiments, the gaseous mixture of waste gas from one or moresterilization chambers 1 may be pumped into gas separator 82 using achamber evacuation pump 2.

In some embodiments, gas separator 82 may contain common water. The gasseparator 82 may be configured to wash waste gas from one or moresterilization chambers 1, with water. As the waste gas comprises agaseous mixture of a sterilization agent, nitrogen gas, and water vapor,the sterilization agent and water vapor may be absorbed by the waterwithin gas separator 82, thereby creating a water gaseous sterilizationagent mixture that may be collected at a bottom section of gas separator82, and the dilution gas, e.g., N₂ gas, may be exhausted at a topsection of gas separator 82.

Gas separator 82 may receive a large waste gas stream flow exhaustingfrom the one or more sterilization chambers 1 via exhaust pumps, and mayretain the waste gas stream inside gas separator 82 for a time of 0.1 to10 minutes to increase the surface area which the waste gas conies incontact with the water contained in the gas separator 82. This allowswater soluble and condensable components in the waste gas stream, inparticular the gaseous sterilizing agent and water vapors, to bedissolved and condensed into the water, forming a water mixture that isrich in sterilization agent, i.e., a water-gaseous sterilization agentmixture. The water-gaseous sterilization agent mixture may then becollected at the bottom portion of the gas separator 82 or in adesignated water mixture receiving tank (not shown). At the same time,the non-water soluble and non-condensable components in the waste gasstream, in particular the dilution gas, e.g., NZ and possibly CO₂ gas,may be separated from the water-gaseous sterilization agent mixture, andmay exit near the top section of the gas separator 82, and may then beexhausted into the atmosphere or to other abatement equipment.

According to some embodiments, gas separator 82 in effect separates thegaseous sterilization agent, e.g., ethylene oxide (ETO) or propyleneoxide (PO) from the dilution gas, e.g., N₂ gas and possibly CO₂ gas, bytaking advantage of the differences in their solubility property inwater. The gaseous sterilization agents are highly soluble in water,i.e., 100 grams ETO dissolve in 1 liter of water, and 400 g PO dissolvein 1 liter of water at 20 degrees Celsius, while dilution gases areconsidered not soluble in water, as only 0.02 g of N₂ dissolve in 1liter of water, and only 1.7 g of CO₂ dissolve in 1 liter of water, atthe same temperature of 20 degrees Celsius. By retaining and interfacingthe waste gas stream with water, the gas separator 82 may dissolve thesterilization agent from the waste gas stream into the water. That is,the clean water in gas separator 82 effectively wash the gas stream tothereby strip the waste gas stream of the sterilization agent and onlyleave clean dilution gas as pan of the waste gas stream. The dilutiongas, e.g., N₂ and possibly CO₂, may then be exhausted into theatmosphere or other abatement equipment through a top portion of gasseparator 82, while the water-gaseous sterilization agent mixture mayexit gas separator 82 through its bottom portion.

According to some embodiments, since system 90 exhausts the dilutiongas, e.g., N₂ gas and possibly CO₂ gas, at an early stage of therecovering process, i.e., the dilution gas exits system 90 from gasseparator 82, system 90 need to treat the dilution gas throughout theentire system, as done, for example, in system 10. This early exhaustionof the dilution gas from the system leads to recovering system 90 beingsmaller compared to the basic recovering system 10, thereby system 90consumes less space, and possibly less energy as the entire procedure issimpler, which are both important advantages of system 90.

In some embodiments, the recovering system may be even smaller, sincethe sterilization agent dissolved in water, i.e., the water-gaseoussterilization agent mixture, may be stored to be processed later by arecovering system. Thus, the one or more sterilization chambers 1, oneor more evacuation pumps 2 and the gas separator 82 along with awater-gaseous sterilization agent mixture container, may be part of aninitial separation system, which separates the dilution gas from thewaste gas thereby leaving, the sterilization agent dissolved in water,while the water-gaseous sterilization agent mixture may later beinputted into a recovering system, which is thus smaller than system 90.

In some embodiments, the water-gaseous sterilization agent mixture fromthe gas separator 82 can be stored at the lower part of the gasseparator 82, stored in separate designated tanks, or may be directlyconnected to evaporator 92.

In some embodiments of the present disclosure, pressure reducing valve 3may reduce the pressure of the water-gaseous sterilization agent mixturepumped into evaporator 92 to a first predefined value such as 1 psi(e.g., pound per square inch), for example, or any suitable pressurevalue, so as to reduce the boiling point temperature of thesterilization agent component in the water-gaseous sterilization agentmixture. The system elements operating at a reduced pressure are shownin reduced pressure region 35 (e.g., inside the dotted rectangle).

In some embodiments of the present disclosure, one or more sterilizationchambers 1 may include an enclosure with the objects and/or items to besterilized configured to withstand pressure variances. One or moresterilization chambers 1 may include inlet and/or outlet ports forremoving air, injecting sterilization agent gases, and removing wastegases.

In some embodiments of the present disclosure, chamber evacuation pump 2may comprise vacuum pumps of various types, capable of removing thewaste gas from one or more sterilization chambers 1. In someembodiments, when there is more than one sterilization chambers 1, eachsterilization chamber may be coupled to a corresponding chamberevacuation pump 2.

In some embodiments of the present disclosure, system 90 may includepressure reduction valve 3 which may be a throttling valve, capable ofreducing and maintaining system pressure in reduced pressure region 35.

In some embodiments, an evaporator 92, which may be coupled to gasseparator 2 via pressure reducing valve 3, may be heated to heat thewater-gaseous sterilization agent mixture to a temperature above boilingpoint temperature of the sterilization agent and above a freezing pointtemperature of the water, to produce gaseous sterilization agent andwater vapor. That is, system 90 has a designated component for heatingthe water-gaseous sterilization agent mixture to produce gaseoussterilization agent and water vapor, unlike system 80 in which H₂O tank300 acts as an evaporator as well as a storage tank for storing watercondensed by H₂O condenser 30.

In some embodiments of the present disclosure, H₂O condenser 30 mayinclude a shell-tube, plate or other type of beat exchanger, which maybe cooled by chilled water or refrigerants. H₂O condenser 30 maycondense and trap water vapor and other contaminants, such as oil usedby chamber evacuation pump 2, H₂O condenser 30 may also allow the cleangaseous sterilization agent to pass into ETO condenser 50.

The condensed water vapor may be received by H₂O tank 300 to be storedtherein. For a pressure of 1 psi, the boding point of water may bereduced to 20 deg C., while the boiling point of ETO is −45 deg C. H₂Ocondenser 30 may be a heat exchanger that chills the gas mixture toabout 4 deg C. to condense the water vapor and contaminants from thesterilization process of the items and/or objects in one or moresterilization chambers 1 such as oil, polymers formed by thesterilization agent, for example, that may be mixed into the watervapor.

An H₂O discharge valve 301 may be used to discharge H₂O and othercontaminants stored in H₂O tank 300. A vacuum release valve 302 may beused to release the vacuum inside reduced pressure region 35 so as tofacilitate discharging H₂O and other contaminants stored in H₂O tank300. Vacuum release valve 302 may be located between H₂O condenser 30and H₂O tank 300, between evaporator 92 and H₂O condenser 30, or atother locations along system 90.

In some embodiments of the present disclosure, the gaseous sterilizationagent with the water vapor removed in reduced pressure region 35, may bepumped into ETO condenser 50 by a separation pump 4 via a separationvalve 4A, which separates reduced pressure region 35 in system 90 fromnormal pressure region 36 in system 90. Separation valve 4A may allowthe gaseous sterilization agent to enter separation pump 4 which pumpsthe gaseous sterilization agent into ETO condenser 50 while raising thepressure of the gaseous sterilization agent to near atmosphericpressure.

In some embodiments of the present disclosure, separation pump 4 mayinclude a vacuum pump capable of maintaining reduced pressures inreduced pressure region 35 (e.g., the region shown from pressurereduction valve 3 to separation pump 4). Separation pump 4 may exhaustgases against atmospheric or near atmospheric pressure in a normalpressure region 36 from separation pump 4 to other abatementequipment/atmosphere as shown in FIG. 9. Separation pump 4 may be avacuum pump that is clean by design, namely that the vacuum pump doesnot introduce additional containments into the gaseous sterilizationagent. Separation pump 4 may include “dry” vacuum pumps, “oil-less” and“near-oil less” vacuum pumps, and/or “diaphragm” vacuum pumps.

In some embodiments of the present disclosure, ETO condenser 50 mayinclude a shell-tube, plate or other type of heat exchanger which may becooled by coolant or refrigerant. ETO condenser 50 may condense and trapsterilization agent vapors, e.g., ETO vapors.

In some embodiments of the present disclosure, ETO condenser 50 maychill the gaseous sterilization agent to a predefined temperature ofabout −110 deg C. slightly higher than the ETO melting point temperatureof −112 deg C.) for condensing the ETO into an ETO liquid. ETO tank 500may be used to store the condensed ETO until reuse. An ETO dischargevalve 501 may be used to discharge ETO for reuse.

In some embodiments, the water in gas separator 82 may be replaced byEthylene Glycol, or a mixture of water and Ethylene Glycol. In someembodiments, gas separator 82 may be cooled to cool the water, EthyleneGlycol, or water-Ethylene Glycol mixture to between 10 to −40 deg C., sothat condensation and solubility of the sterilization agent, ETO, in thewater, Ethylene Glycol or water-Ethylene Glycol mixture is furtherimproved.

In some embodiments, the water-gaseous sterilization agent mixture fromgas separator 82 can be stored at the lower part of the gas separator82, stored in separate designated tanks, may be directly connected toH₂O tank 300, or may be directly connected to evaporator 92.

In both of systems 80 and 90, the dilution gas, e.g., N₂ and CO₂, isexhausted out of either of these systems at the beginning of therecovering process, such that the gas stream entering the reducedpressure region 35 includes no dilution gas and only includes awater-gaseous sterilization agent mixture (i.e., condensable water vaporand gaseous sterilization agent). There are several benefits forremoving the dilution gas at the beginning of the process instead ofexhausting it at the end of the recovering process or even during theprocess at a later stage than that of gas separator 82, a few of thembeing

1. increasing efficiency of the condensers. Since the thermalconductivity of the non-condensable dilution gas is extremely lowcompared to that of the material of the heat transfer surface in thecondensers (specifically, 25 mW/(m*K) for N₂, 15 W/(m*K) for CO₂,compared to 15,000 mW/(m*K) for stainless steel and 386,000 mW/(m*K) forcopper, whereby mW/(m*K) means that for every meter thickness ofmaterial at 1 Kelvin of temperature difference between the hot side andcold side, heat can pass through at a rate of 25 milliwatts). Thenon-condensable dilution gas having very low thermal conductively mayform a boundary layer on the heat transfer surface of the condensers,thereby to behave like an insulator and hinder the waste gas stream frombeing further cooled and condensed by the condenser heat transfersurface material. By removing the non-condensable dilution gas from theWaste gas stream, the efficiency of the condensers is greatly increasedby as much as several orders of magnitude. The result is that muchsmaller sized condensers may be employed in either of systems 80 or 90.2. Eliminating the need to cool the non-condensable dilution gases tothe very low temperature of the second condenser (e.g., ETO condenser50). As implemented in either of systems 80 or 90, after thewater-gaseous sterilization agent mixture passes the first condenser,e.g., H₂O condenser 30. the only gas remaining in the gas stream mixtureis the gaseous sterilization agent. This reduces the total mass of thegas flow to the second condenser, and thus reduces the cooling energyrequired to cool the second condenser.3. Eliminating the need to proportionally enlarge the condensers, pump,and cooling systems to handle the larger peak flow. By temporaryretaining the gaseous sterilization agent in the new water-gaseoussterilization agent mixture that is thus rich with water solublesterilization agent, the only component that needs to be changed in sizeto handle the large peak flow is the gas separator. e.g., gas separator82, which may be easily acquired at a reasonable cost. After the wastegas stream passes through the gas separator, the gaseous sterilizationagent is dissolved in the water to produce a water-gaseous sterilizationagent mixture, such that the sterilization agent is contained in liquidform. When the gaseous sterilization agent is transformed from gas formto liquid form, the volume of the gaseous sterilizing agent is reducedby 3 orders of magnitude (e.g., from 1.67 liters/gram to 1.13 ml/gram),making it easily storable in storage tanks. Storing the gaseoussterilization agent in liquid form, enables continuing with therecovering process at a later time, by generating a new gas streameither by H₂O tank 300 in system 80, or by evaporator 92 in system 90.Thus, the rest of the system's components, that are more expensive toacquire, do not need to be enlarged to simultaneously handle the largepeak flow generated by the multiple large sterilization chambers 1.Rather, the condenser, valves, corresponding cooling systems, and theseparation pump, may be sized to handle the “average” flow rate from theone or more sterilization chambers 1. This is particularly advantageousin terms of sizing reduction of the systems, since the normalsterilization chamber operates in “batch” operations. In one “batch”operation, or one sterilization cycle, the time of exhausting wastesterilization gas only occupies 2˜4% of the total operation time. Withthe ability to store the gaseous sterilization agent in liquid form, itmay be processed at a later time in a steady, smaller and continuousrate. This means that other than the gas separator, the rest of eitherof systems 80 or 90, may be sized to treat only 1/20 to 1/50 of the peakgaseous sterilizing agent flow rate, which presents very significantsizing reduction of either of the systems.

Therefore, the feature of the gas separator, which enables exhaustion ofdilution gas at an early stage from the recovering system, as well asenables storing the sterilization agent in liquid form for laterprocess, provides the sizing and the initial capital cost of acquiringand installing either of systems 80 or 90 to handle large peak flowsfrom multiple sterilization chambers to be significantly reduced to afraction of what it would have been without the new gas separatorfeature.

In addition, with this new gas separator feature, the operational costof either of systems 80 Or 90 is also significantly reduced, becausethere is no longer a need to cool the non-condensable dilution gas. Thiscost saving is amplified because the cost of cooling increasessignificantly as the intended cooling temperature decreases. The cost ofcooling the dilution gases to the very low temperature of the secondcondenser is more than ten times than that of cooling the firstcondenser. Therefore, by removing the non-condensable gas from enteringthe second condenser, significant cooling cost reduction can beachieved.

In some embodiments, recovering system 80 may be implemented, when theone or more sterilization systems are relatively small, e.g., thechamber size is less than 150 liters, whereas recovering; system 90 maybe implemented when the one or more sterilization systems are relativelylarge, e.g., chamber size may be greater or equal to 150 liters, inother embodiments, other chamber sizes may be considered small or large.

FIG. 10 is a flowchart depicting a method 1000 for recovering asterilization agent from a waste gaseous mixture from one or moresterilization chambers, in accordance with some embodiments of thepresent disclosure.

Method 1000 may include receiving 1010 a waste gas from one or moresterilization chambers. The waste gas may include a gaseous mixture of asterilization agent, nitrogen gas, and water vapor.

Method 1000 may include washing 1015 the gaseous mixture with water by agas separator, thereby absorbing the sterilization agent and water vaporin the water, creating a water-gaseous sterilization agent mixture.

Method 1000 may include collecting 1020 the water-gaseous sterilizationagent mixture at a bottom section of the gas separator and exhaustingthe nitrogen gas at a top section of the gas separator.

Method 1000 may include reducing 1025 a pressure of the water-gaseoussterilization agent mixture to a first predefined pressure so as toreduce a boiling point temperature of the sterilization agent to below afreezing point temperature of water in the water-gaseous sterilizationagent mixture.

Method 1000 may include heating 1030 the water gaseous sterilizationagent mixture to a temperature above boiling point temperature of thesterilization agent and above a freezing point temperature of the waterto produce gaseous sterilization agent and water vapor.

Method 1000 may include cooling 1035 the gaseous sterilization agent andwater vapor with the pressure at the first predefined pressure by afirst condenser to a temperature below a boiling point temperature andabove the freezing point temperature of the water vapor, and removingcondensed water vapor from the gaseous sterilization agent.

Method 1000 may include raising 1040 the pressure of the gaseoussterilization agent by a separation pump, to a second predefinedpressure greater than the first predefined pressure so as to elevate aboiling point temperature of the sterilization agent said separationpump being coupled to the first condenser, or the upper portion of thefirst tank.

Method 1000 may include cooling 1045 the gaseous sterilization agent atthe second predefined pressure, by a second condenser, to a temperaturebelow the boiling point temperature and above a freezing pointtemperature of the sterilization agent causing the sterilization agentto condense into a liquid.

Method 1000 may include collecting 1050 the liquid sterilization agentfor reuse.

It should be understood with respect to any flowchart referenced hereinthat the division of the illustrated method into discrete operationsrepresented by blocks of the flowchart has been selected for convenienceand clarity only. Alternative division of the illustrated method intodiscrete operations is possible with equivalent results. Suchalternative division of the illustrated method into discrete operationsshould be understood as representing other embodiments of theillustrated method.

Similarly, it should be understood that, unless indicated otherwise, theillustrated order of execution of the operations represented by blocksof any flowchart referenced herein has been selected for convenience andclarity only. Operations of the illustrated method may be executed in analternative order, or concurrently, with equivalent results. Suchreordering of operations of the illustrated method should be understoodas representing other embodiments of the illustrated method.

Different embodiments are disclosed herein. Features of certainembodiments may be combined with features of other embodiments; thuscertain embodiments may be combinations of features of multipleembodiments. The foregoing description of the embodiments of thedisclosure has been presented for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit thedisclosure to the precise form disclosed. It should be appreciated bypersons skilled in the art that many modifications, variations,substitutions, changes, and equivalents are possible in light of theabove teaching. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the disclosure.

While certain features of the disclosure have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the disclosure.

1. A system for recovering a sterilization agent from a waste gaseousmixture, the system comprising: a gas separator configured to wash wastegas from one or more sterilization chambers, with water, the waste gascomprising a gaseous mixture of a sterilization agent, inert dilutiongases, and water vapor, thereby the sterilization agent and water vaporare absorbed by the water creating a water-gaseous sterilization agentmixture that is collected at a bottom section of the gas separator, andthe inert dilution gases are exhausted at a top section of the gasseparator; a pressure reducing valve for reducing a pressure of thewater-gaseous sterilization agent mixture to a first predefinedpressure; a first tank or a gas evaporator, coupled to the pressurereducing valve, configured to receive the water-gaseous sterilizationagent mixture and to heat the water-gaseous sterilization agent mixtureto a temperature above bailing point temperature of the sterilizationagent and above a freezing point temperature of the water to producegaseous sterilization agent and water vapor; a first condenserconfigured to receive gaseous sterilization agent and water vapor viathe first tank or the gas evaporator, and to cool the gaseoussterilization agent and water vapor to a temperature below a boilingpoint temperature and above a freezing point temperature of the watervapor at the first predefined pressure to produce condensed water vaporand to separate the gaseous sterilization agent from the condensed watervapor; a water tank, coupled to the first condenser, configured toreceive the condensed water vapor, wherein when the first tank heats thewater-gaseous sterilization agent mixture, the water tank is the sametank as the first tank, and when the gas evaporator heats thewater-gaseous sterilization agent mixture, the water tank is in additionto the first tank; a separation pump coupled to the first condenser forraising the pressure of the gaseous sterilization agent to a secondpredefined pressure; a second condenser, configured to receive thegaseous sterilization agent from the separation pump, to cool thegaseous sterilization agent to a temperature below a boiling pointtemperature and above a freezing point temperature of the sterilizationagent at the second predefined pressure causing, the sterilization agentto condense into a liquid; and a second tank, coupled to the secondcondenser, for storing the liquid sterilization anent.
 2. The systemaccording to claim 1, wherein the sterilization agent comprises ethyleneoxide (ETO).
 3. The system according to claim 2, wherein the firstpredefined pressure is 1 pound per square inch and the second predefinedpressure is atmospheric pressure.
 4. The system according to claim 3,wherein the boiling point temperature of the water vapor is 20 deg C.when the pressure of the gaseous mixture is 1 psi.
 5. The systemaccording to claim 3, wherein the boiling point temperature of the ETOis 10 deg C. when the pressure of the gaseous mixture is atmosphericpressure.
 6. The system according to claim 1, wherein the sterilizationagent is propylene oxide.
 7. The system according to claim 1, furthercomprising a chamber evacuation pump coupled to the gas separator forpumping the waste gas into the gas separator.
 8. The system according toclaim 1, further comprising an exhaust warmer and a freezer economizerfor recovering cooling energy in the system.
 9. The system according toclaim 1, further comprising one or more H₂O freezers coupled to thefirst condenser and the separation pump, and wherein each of the one ormore H₂O freezers freezes H₂O molecules in the water vapor to a freezersurface.
 10. The system according to claim 9, wherein at least two H₂Ofreezers from the one or more H₂O freezers are connected in parallel,coupled between the first condenser and the separation pump.
 11. Thesystem according to claim 1, further comprising one or more ETO freezerscoupled to the second condenser for trapping residual vapors of thesterilization agent.
 12. The system according to claim 11, wherein atleast taw ETO freezers from the one or more ETO freezers are connectedin parallel.
 13. The system according to claim 1, further comprising oneor more ETO pre-condensers placed in series before the second condenser,wherein each of the one or more pre-condensers have progressively lowertemperatures above the temperature of the second condenser.
 14. A methodfor recovering a sterilization agent from a waste gaseous mixture, themethod comprising: receiving a waste gas from one or more sterilizationchambers, the waste gas comprising a gaseous mixture of a sterilizationagent, inert dilution gases, and water vapor; washing the gaseousmixture with water by a gas separator, thereby absorbing thesterilization agent and water vapor in the water, creating awater-gaseous sterilization agent mixture; collecting the water gaseoussterilization agent mixture at a bottom section of the gas separator,and exhausting the inert dilution gases at a top section of the gasseparator; reducing a pressure of die water-gaseous sterilization agentmixture to a first predefined pressure so as to reduce a boiling pointtemperature of the sterilization agent to below a freezing pointtemperature of water in the water-gaseous sterilization agent mixture;heating the water-gaseous sterilization agent mixture to a temperatureabove boiling point temperature of the sterilization agent and above afreezing point temperature of the water to produce gaseous sterilizationagent and water vapor; cooling the gaseous sterilization agent and watervapor with the pressure at the first predefined pressure by a firstcondenser, to a temperature below a boiling point temperature and abovethe freezing point temperature of the water vapor, and removingcondensed water vapor from the gaseous sterilization agent; raising thepressure of the gaseous sterilization agent by a separation pump, to asecond predefined pressure greater than the first predefined pressure soas to elevate a boiling point temperature of the sterilization agent,said separation pump being coupled to the first condenser, or the upperportion of the first tank; cooling the gaseous mixture at the secondpredefined pressure, by a second condenser, to a temperature below theboiling point temperature and above a freezing point temperature of thesterilization agent causing the sterilization agent to condense into aliquid, thereby collecting the liquid sterilization agent for reuse. 15.The method according to claim 14, wherein the sterilization agentcomprises ethylene oxide (ETO).
 16. The method according to claim 15,wherein the first predefined pressure is pound per square inch (psi) andthe second predefined pressure is atmospheric pressure.
 17. The methodaccording to claim 16, wherein the boiling point temperature of thewater vapor is 20 deg C. when the pressure of the gaseous mixture is 1psi.
 18. The method according to claim 16 wherein the boiling pointtemperature of the ETO is 10 deg C. when the pressure of the gaseousmixture is atmospheric pressure.
 19. The method according to claim 14,wherein the sterilization agent is propylene oxide.
 20. The methodaccording to claim 14, wherein exhausting inert dilution gases comprisesdischarging nitrogen gas or CO₂ gas or a combination thereof, to theatmosphere or collecting the exhausted inert dilution gases comprisingnitrogen gas or CO₂ gas or a combination thereof, for reuse.
 21. Themethod according to claim 14, further comprising recovering coolingenergy in the system by using an exhaust warmer and a freezereconomizer.
 22. The method according to claim 14, further comprising;freezing H₂O molecules in the water vapor to a freezer surface of one ormore H₂O freezers.
 23. The method according to claim 22, wherein atleast two H₂O freezers from the one or more H₂O freezers are connectedin parallel, and further comprising defrosting at least one of the H₂Ofreezers from the at least two parallel H₂O freezers.
 24. The methodaccording to claim 14, further comprising trapping residual vapors ofthe sterilization agent using one or more ETO freezers coupled to thesecond condenser.
 25. The method according to claim 24 wherein at leasttwo ETO freezers from the one or more ILO freezers are cornice ted inparallel, and further comprising defrosting at least one of the ETOfreezers from the at least two parallel ETO freezers.
 26. The methodaccording to claim 14, further comprising setting the temperatures ofeach of one or more ETO pre-condensers placed in series before thesecond condenser to progressively lower temperatures above thetemperature of the second condenser.